Antennas transmit and receive radio-frequency (RF) signals to communicate information. These radio-frequency signals enable users to talk with friends, download or upload information, share pictures, remotely control household devices, and receive global positioning information. Sometimes an electronic device includes multiple antennas that utilize multiple-input multiple-output (MIMO) techniques, such as spatial diversity or spatial multiplexing, to improve wireless communication performance. To implement spatial diversity, the multiple antennas transmit or receive redundant streams of information in parallel along different spatial paths associated with each of the antennas. This increases a reliability associated with transferring information between devices and further increases an effective wireless communication range. To implement spatial multiplexing, the multiple antennas transmit or receive different streams of information in parallel along the different spatial paths. This results in increased throughput for wireless communications.
Implementing multiple antennas that support MIMO techniques within the electronic device, however, can be challenging. Spatial constraints of the electronic device can, for example, limit physical distances between the multiple antennas. Without sufficient antenna spacing, the multiple antennas couple together and interfere with each other. The resulting interference can cause operational performance of the individual antennas to be dependent upon each other, which is undesirable for implementing MIMO techniques. Consequently, it may be impractical for some electronic devices that place a premium on small size to have sufficient space to achieve a target amount of isolation between the multiple antennas for MIMO applications.